ajs 14 crankcase breather

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ajs 14 crankcase breather

Postby Bill2181 » Wed Jan 20, 2021 5:31 pm

Hi All, I need your help. The rotor in the crankcase relief valve is free to rotate on the crankshaft. Should it be? There is a very narrow (1mm) slit in the crankshaft and a broader slit on the inside edge of the rotor, ? keyway. There is also a bolt in the crankcase which I would guess should lock the rotor, but the bolt is too short anyway. Does anyone have a diagram showing how it should be? Many thanks in anticipation.
Bill
Last edited by Bill2181 on Wed Jan 20, 2021 6:34 pm, edited 1 time in total.

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Re: ajs 14 crankcase breather

Postby SPRIDDLER » Wed Jan 20, 2021 6:29 pm

Sorry Bill, can't help with your question but it's not reckoned to be a good idea to put your email address on an open forum
If a member wants to email you they can click on your name beside your post, then click on Profile and the page below comes up. They can click on where i've put the arrow to send you an email. Only subscribing members can access that page so it provide a bit of security from scammers and phishers.



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Re: ajs 14 crankcase breather

Postby clanger9 » Wed Jan 20, 2021 9:47 pm

Hi Bill,

Yes, it's a keyway. The rotor should bey keyed onto the crankshaft with key 017602 (available from club spares).

This diagram shows how the bolted breather tube is supposed to fit:
http://archives.jampot.dk/technical/Cut ... 7-1964.jpg

You might have the later breather with the separate bolt (and cast-in breather tube), in which case it's just a simple bolt that holds the stator in place. Lots of useful pics in this thread:
viewtopic.php?f=15&t=16585&p=150416&#p150328
1989 Moto Morini Dart 350
1993 Ducati 750SS

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Re: ajs 14 crankcase breather

Postby Bill2181 » Thu Jan 21, 2021 3:16 pm

Thank you clanger9, It all begins to make sense apart from the fact that this engine has two ball races, and the rotor, being sandwiched between them makes keying to the crankshaft well nigh impossible. I therefor conclude that some previous owner has fitted a ball rather than two part roller race, and let the breather to do its own thing. There was no signs of a key when stripped. I shall duly order the correct bearing.
Many thanks for your help.

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Re: ajs 14 crankcase breather

Postby clanger9 » Thu Jan 21, 2021 3:39 pm

Hi Bill,

Glad that's helpful! Early engines did have two ball races - it's a mystery how they were assembled at the factory! This arrangement was subsequently changed to an outer ball bearing and inner roller bearing, which makes a lot more sense.

Here's a sketch I made that shows how it's supposed to fit together. It's an unusual arrangement, so it's no wonder it is sometimes assembled incorrectly...

lightweight_main_bearings.png
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